<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>switch没有break的话</title>
</head>

<body>
    <script>
        let x = 0;
        switch (1) {
            case 1: ++x;
            case 2: ++x;
            case 3: --x;
        }
        //最后输出1，原因在于swich没有break会继续执行
        console.log(x);//1
    </script>
</body>

</html>